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<div class="titlepage"><div><div><h4 class="title">
<a name="boost_regex.ref.concepts.traits_concept"></a><a class="link" href="traits_concept.html" title="Traits Class Requirements">Traits Class
        Requirements</a>
</h4></div></div></div>
<p>
          There are two sets of requirements for the <code class="computeroutput"><span class="identifier">traits</span></code>
          template argument to <a class="link" href="../basic_regex.html" title="basic_regex"><code class="computeroutput"><span class="identifier">basic_regex</span></code></a>: a minimal interface
          (which is part of the regex standardization proposal), and an optional
          Boost-specific enhanced interface.
        </p>
<h5>
<a name="boost_regex.ref.concepts.traits_concept.h0"></a>
          <span class="phrase"><a name="boost_regex.ref.concepts.traits_concept.minimal_requirements"></a></span><a class="link" href="traits_concept.html#boost_regex.ref.concepts.traits_concept.minimal_requirements">Minimal
          requirements.</a>
        </h5>
<p>
          In the following table <code class="computeroutput"><span class="identifier">X</span></code>
          denotes a traits class defining types and functions for the character container
          type <code class="computeroutput"><span class="identifier">charT</span></code>; <span class="emphasis"><em>u</em></span>
          is an object of type <code class="computeroutput"><span class="identifier">X</span></code>;
          <span class="emphasis"><em>v</em></span> is an object of type <code class="computeroutput"><span class="keyword">const</span>
          <span class="identifier">X</span></code>; <span class="emphasis"><em>p</em></span> is
          a value of type <code class="computeroutput"><span class="keyword">const</span> <span class="identifier">charT</span><span class="special">*</span></code>; <span class="emphasis"><em>I1</em></span> and <span class="emphasis"><em>I2</em></span>
          are Input Iterators; <span class="emphasis"><em>c</em></span> is a value of type <code class="computeroutput"><span class="keyword">const</span> <span class="identifier">charT</span></code>;
          <span class="emphasis"><em>s</em></span> is an object of type <code class="computeroutput"><span class="identifier">X</span><span class="special">::</span><span class="identifier">string_type</span></code>;
          <span class="emphasis"><em>cs</em></span> is an object of type <code class="computeroutput"><span class="keyword">const</span>
          <span class="identifier">X</span><span class="special">::</span><span class="identifier">string_type</span></code>; <span class="emphasis"><em>b</em></span> is
          a value of type <code class="computeroutput"><span class="keyword">bool</span></code>; <span class="emphasis"><em>I</em></span>
          is a value of type <code class="computeroutput"><span class="keyword">int</span></code>; <span class="emphasis"><em>F1</em></span>
          and <span class="emphasis"><em>F2</em></span> are values of type <code class="computeroutput"><span class="keyword">const</span>
          <span class="identifier">charT</span><span class="special">*</span></code>;
          and <span class="emphasis"><em>loc</em></span> is an object of type <code class="computeroutput"><span class="identifier">X</span><span class="special">::</span><span class="identifier">locale_type</span></code>.
        </p>
<div class="informaltable"><table class="table">
<colgroup>
<col>
<col>
<col>
</colgroup>
<thead><tr>
<th>
                  <p>
                    Expression
                  </p>
                </th>
<th>
                  <p>
                    Return type
                  </p>
                </th>
<th>
                  <p>
                    Assertion / Note Pre / Post condition
                  </p>
                </th>
</tr></thead>
<tbody>
<tr>
<td>
                  <p>
                    X::char_type
                  </p>
                </td>
<td>
                  <p>
                    charT
                  </p>
                </td>
<td>
                  <p>
                    The character container type used in the implementation of class
                    template basic_regex.
                  </p>
                </td>
</tr>
<tr>
<td>
                  <p>
                    X::size_type
                  </p>
                </td>
<td>
                </td>
<td>
                  <p>
                    An unsigned integer type, capable of holding the length of a
                    null-terminated string of charT's.
                  </p>
                </td>
</tr>
<tr>
<td>
                  <p>
                    X::string_type
                  </p>
                </td>
<td>
                  <p>
                    std::basic_string&lt;charT&gt; or std::vector&lt;charT&gt;
                  </p>
                </td>
<td>
                </td>
</tr>
<tr>
<td>
                  <p>
                    X::locale_type
                  </p>
                </td>
<td>
                  <p>
                    Implementation defined
                  </p>
                </td>
<td>
                  <p>
                    A copy constructible type that represents the locale used by
                    the traits class.
                  </p>
                </td>
</tr>
<tr>
<td>
                  <p>
                    X::char_class_type
                  </p>
                </td>
<td>
                  <p>
                    Implementation defined
                  </p>
                </td>
<td>
                  <p>
                    A bitmask type representing a particular character classification.
                    Multiple values of this type can be bitwise-or'ed together to
                    obtain a new valid value.
                  </p>
                </td>
</tr>
<tr>
<td>
                  <p>
                    X::length(p)
                  </p>
                </td>
<td>
                  <p>
                    X::size_type
                  </p>
                </td>
<td>
                  <p>
                    Yields the smallest i such that p[i] == 0. Complexity is linear
                    in i.
                  </p>
                </td>
</tr>
<tr>
<td>
                  <p>
                    v.translate(c)
                  </p>
                </td>
<td>
                  <p>
                    X::char_type
                  </p>
                </td>
<td>
                  <p>
                    Returns a character such that for any character d that is to
                    be considered equivalent to c then v.translate(c) == v.translate(d).
                  </p>
                </td>
</tr>
<tr>
<td>
                  <p>
                    v.translate_nocase(c)
                  </p>
                </td>
<td>
                  <p>
                    X::char_type
                  </p>
                </td>
<td>
                  <p>
                    For all characters C that are to be considered equivalent to
                    c when comparisons are to be performed without regard to case,
                    then v.translate_nocase(c) == v.translate_nocase(C).
                  </p>
                </td>
</tr>
<tr>
<td>
                  <p>
                    v.transform(F1, F2)
                  </p>
                </td>
<td>
                  <p>
                    X::string_type
                  </p>
                </td>
<td>
                  <p>
                    Returns a sort key for the character sequence designated by the
                    iterator range [F1, F2) such that if the character sequence [G1,
                    G2) sorts before the character sequence [H1, H2) then v.transform(G1,
                    G2) &lt; v.transform(H1, H2).
                  </p>
                </td>
</tr>
<tr>
<td>
                  <p>
                    v.transform_primary(F1, F2)
                  </p>
                </td>
<td>
                  <p>
                    X::string_type
                  </p>
                </td>
<td>
                  <p>
                    Returns a sort key for the character sequence designated by the
                    iterator range [F1, F2) such that if the character sequence [G1,
                    G2) sorts before the character sequence [H1, H2) when character
                    case is not considered then v.transform_primary(G1, G2) &lt;
                    v.transform_primary(H1, H2).
                  </p>
                </td>
</tr>
<tr>
<td>
                  <p>
                    v.lookup_classname(F1, F2)
                  </p>
                </td>
<td>
                  <p>
                    X::char_class_type
                  </p>
                </td>
<td>
                  <p>
                    Converts the character sequence designated by the iterator range
                    [F1,F2) into a bitmask type that can subsequently be passed to
                    isctype. Values returned from lookup_classname can be safely
                    bitwise or'ed together. Returns 0 if the character sequence is
                    not the name of a character class recognized by X. The value
                    returned shall be independent of the case of the characters in
                    the sequence.
                  </p>
                </td>
</tr>
<tr>
<td>
                  <p>
                    v.lookup_collatename(F1, F2)
                  </p>
                </td>
<td>
                  <p>
                    X::string_type
                  </p>
                </td>
<td>
                  <p>
                    Returns a sequence of characters that represents the collating
                    element consisting of the character sequence designated by the
                    iterator range [F1, F2). Returns an empty string if the character
                    sequence is not a valid collating element.
                  </p>
                </td>
</tr>
<tr>
<td>
                  <p>
                    v.isctype(c, v.lookup_classname (F1, F2))
                  </p>
                </td>
<td>
                  <p>
                    bool
                  </p>
                </td>
<td>
                  <p>
                    Returns true if character c is a member of the character class
                    designated by the iterator range [F1, F2), false otherwise.
                  </p>
                </td>
</tr>
<tr>
<td>
                  <p>
                    v.value(c, I)
                  </p>
                </td>
<td>
                  <p>
                    int
                  </p>
                </td>
<td>
                  <p>
                    Returns the value represented by the digit c in base I if the
                    character c is a valid digit in base I; otherwise returns -1.
                    [Note: the value of I will only be 8, 10, or 16. -end note]
                  </p>
                </td>
</tr>
<tr>
<td>
                  <p>
                    u.imbue(loc)
                  </p>
                </td>
<td>
                  <p>
                    X::locale_type
                  </p>
                </td>
<td>
                  <p>
                    Imbues u with the locale loc, returns the previous locale used
                    by u if any.
                  </p>
                </td>
</tr>
<tr>
<td>
                  <p>
                    v.getloc()
                  </p>
                </td>
<td>
                  <p>
                    X::locale_type
                  </p>
                </td>
<td>
                  <p>
                    Returns the current locale used by v if any.
                  </p>
                </td>
</tr>
</tbody>
</table></div>
<h5>
<a name="boost_regex.ref.concepts.traits_concept.h1"></a>
          <span class="phrase"><a name="boost_regex.ref.concepts.traits_concept.additional_optional_requirements"></a></span><a class="link" href="traits_concept.html#boost_regex.ref.concepts.traits_concept.additional_optional_requirements">Additional
          Optional Requirements</a>
        </h5>
<p>
          The following additional requirements are strictly optional, however in
          order for <a class="link" href="../basic_regex.html" title="basic_regex"><code class="computeroutput"><span class="identifier">basic_regex</span></code></a>
          to take advantage of these additional interfaces, all of the following
          requirements must be met; <a class="link" href="../basic_regex.html" title="basic_regex"><code class="computeroutput"><span class="identifier">basic_regex</span></code></a> will detect the presence
          or absence of the member <code class="computeroutput"><span class="identifier">boost_extensions_tag</span></code>
          and configure itself appropriately.
        </p>
<div class="informaltable"><table class="table">
<colgroup>
<col>
<col>
<col>
</colgroup>
<thead><tr>
<th>
                  <p>
                    Expression
                  </p>
                </th>
<th>
                  <p>
                    Result
                  </p>
                </th>
<th>
                  <p>
                    Assertion / Note Pre / Post condition
                  </p>
                </th>
</tr></thead>
<tbody>
<tr>
<td>
                  <p>
                    X::boost_extensions_tag
                  </p>
                </td>
<td>
                  <p>
                    An unspecified type.
                  </p>
                </td>
<td>
                  <p>
                    When present, all of the extensions listed in this table must
                    be present.
                  </p>
                </td>
</tr>
<tr>
<td>
                  <p>
                    v.syntax_type(c)
                  </p>
                </td>
<td>
                  <p>
                    regex_constants::syntax_type
                  </p>
                </td>
<td>
                  <p>
                    Returns a symbolic value of type regex_constants::syntax_type
                    that signifies the meaning of character c within the regular
                    expression grammar.
                  </p>
                </td>
</tr>
<tr>
<td>
                  <p>
                    v.escape_syntax_type(c)
                  </p>
                </td>
<td>
                  <p>
                    regex_constants::escape_syntax_type
                  </p>
                </td>
<td>
                  <p>
                    Returns a symbolic value of type regex_constants::escape_syntax_type,
                    that signifies the meaning of character c within the regular
                    expression grammar, when c has been preceded by an escape character.
                    Precondition: if b is the character preceding c in the expression
                    being parsed then: <code class="computeroutput"><span class="identifier">v</span><span class="special">.</span><span class="identifier">syntax_type</span><span class="special">(</span><span class="identifier">b</span><span class="special">)</span> <span class="special">==</span>
                    <span class="identifier">syntax_escape</span></code>
                  </p>
                </td>
</tr>
<tr>
<td>
                  <p>
                    v.translate(c, b)
                  </p>
                </td>
<td>
                  <p>
                    X::char_type
                  </p>
                </td>
<td>
                  <p>
                    Returns a character d such that: for any character d that is
                    to be considered equivalent to c then <code class="computeroutput"><span class="identifier">v</span><span class="special">.</span><span class="identifier">translate</span><span class="special">(</span><span class="identifier">c</span><span class="special">,</span><span class="keyword">false</span><span class="special">)==</span><span class="identifier">v</span><span class="special">.</span><span class="identifier">translate</span><span class="special">(</span><span class="identifier">d</span><span class="special">,</span><span class="keyword">false</span><span class="special">)</span></code>. Likewise for all characters
                    C that are to be considered equivalent to c when comparisons
                    are to be performed without regard to case, then <code class="computeroutput"><span class="identifier">v</span><span class="special">.</span><span class="identifier">translate</span><span class="special">(</span><span class="identifier">c</span><span class="special">,</span><span class="keyword">true</span><span class="special">)==</span><span class="identifier">v</span><span class="special">.</span><span class="identifier">translate</span><span class="special">(</span><span class="identifier">C</span><span class="special">,</span><span class="keyword">true</span><span class="special">)</span></code>.
                  </p>
                </td>
</tr>
<tr>
<td>
                  <p>
                    v.toi(I1, I2, i)
                  </p>
                </td>
<td>
                  <p>
                    An integer type capable of holding either a charT or an int.
                  </p>
                </td>
<td>
                  <p>
                    Behaves as follows: if <code class="computeroutput"><span class="identifier">p</span>
                    <span class="special">==</span> <span class="identifier">q</span></code>
                    or if <code class="computeroutput"><span class="special">*</span><span class="identifier">p</span></code>
                    is not a digit character then returns -1. Otherwise performs
                    formatted numeric input on the sequence [p,q) and returns the
                    result as an int. Postcondition: either p == q or *p is a non-digit
                    character.
                  </p>
                </td>
</tr>
<tr>
<td>
                  <p>
                    v.error_string(I)
                  </p>
                </td>
<td>
                  <p>
                    std::string
                  </p>
                </td>
<td>
                  <p>
                    Returns a human readable error string for the error condition
                    i, where i is one of the values enumerated by type regex_constants::error_type.
                    If the value <span class="emphasis"><em>I</em></span> is not recognized then returns
                    the string "Unknown error" or a localized equivalent.
                  </p>
                </td>
</tr>
<tr>
<td>
                  <p>
                    v.tolower(c)
                  </p>
                </td>
<td>
                  <p>
                    X::char_type
                  </p>
                </td>
<td>
                  <p>
                    Converts c to lower case, used for Perl-style \l and \L formatting
                    operations.
                  </p>
                </td>
</tr>
<tr>
<td>
                  <p>
                    v.toupper(c)
                  </p>
                </td>
<td>
                  <p>
                    X::char_type
                  </p>
                </td>
<td>
                  <p>
                    Converts c to upper case, used for Perl-style \u and \U formatting
                    operations.
                  </p>
                </td>
</tr>
</tbody>
</table></div>
</div>
<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
<td align="left"></td>
<td align="right"><div class="copyright-footer">Copyright © 1998-2013 John Maddock<p>
        Distributed under the Boost Software License, Version 1.0. (See accompanying
        file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
      </p>
</div></td>
</tr></table>
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